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Multiple H⁺ sensors mediate the extracellular acidification-induced [Ca²⁺]_i elevation in cultured rat ventricular cardiomyocytes.

ABSTRACT: Acidosis has been known to cause "Ca²⁺ transients", however, the mechanism is still uncertain. Here, we demonstrated that multiple H⁺ sensors, such as ASICs, TRPV1 and proton-sensing G protein coupled receptors (GPCRs) are involved in extracellular acidification-induced intracellular calcium ([Ca²⁺]_i) elevation. By using calcium imaging measures, we observed that both ASIC and TRPV1 channels inhibitors suppressed the [Ca²⁺]_i elevation induced by extracellular acidosis in cultured rat cardiac myocytes. Then, both channels mRNA and proteins were identified by RT-PCR, western blotting and immunofluorescence. ASIC-like and TRPV1-like currents were induced by extracellular acidification, suggesting that functional ASIC and TRPV1 channels jointly mediated extracellular calcium entry. Furthermore, either pre-exhaustion of sarcoplasmic reticulum (SR) Ca²⁺ with thapsigargin or IP₃ receptor blocker 2-APB or PLC inhibitor U73122 significantly attenuated the elevation of [Ca²⁺]_i, indicating that the intracellular Ca²⁺ stores and the PLC-IP₃ signaling also contributed to the acidosis-induced elevation of [Ca²⁺]_i. By using genetic and pharmacological approaches, we identified that ovarian cancer G protein-coupled receptor 1 (OGR1) might be another main component in acidosis-induced release of [Ca²⁺]_i. These results suggest that multiple H⁺-sensitive receptors are involved in "Ca²⁺ transients" induced by acidosis in the heart.

SUBMITTER: Hu YL

PROVIDER: S-EPMC5362981 | biostudies-literature | 2017 Mar

REPOSITORIES: biostudies-literature

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Multiple H+ sensors mediate the extracellular acidification-induced [Ca2+]i elevation in cultured rat ventricular cardiomyocytes.

Hu Yuan-Lang YL Mi Xue X Huang Chao C Wang Hui-Fang HF Song Jian-Ren JR Shu Qing Q Ni Lan L Chen Jian-Guo JG Wang Fang F Hu Zhuang-Li ZL

Scientific reports 20170323

Acidosis has been known to cause "Ca2+ transients", however, the mechanism is still uncertain. Here, we demonstrated that multiple H+ sensors, such as ASICs, TRPV1 and proton-sensing G protein coupled receptors (GPCRs) are involved in extracellular acidification-induced intracellular calcium ([Ca2+]i) elevation. By using calcium imaging measures, we observed that both ASIC and TRPV1 channels inhibitors suppressed the [Ca2+]i eleva ...[more]

PMID: 28332558

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Project description:AimsPhospholamban (PLB) is the key regulator of the cardiac Ca2+ pump (SERCA2a)-mediated sarcoplasmic reticulum Ca2+ stores. We recently reported that PLB is highly concentrated in the nuclear envelope (NE) from where it can modulate perinuclear Ca2+ handling of the cardiomyocytes (CMs). Since inositol 1,4,5-trisphosphate (IP3) receptor (IP3R) mediates nuclear Ca2+ release, we examined whether the nuclear pool of PLB regulates IP3-induced nuclear Ca2+ handling.Methods and resultsFluo-4 based confocal Ca2+ imaging was performed to measure Ca2+ dynamics across both nucleus and cytosol in saponin-permeabilized CMs isolated from wild-type (WT) or PLB-knockout (PLB-KO) mice. At diastolic intracellular Ca2+ ([Ca2+]i = 100 nM), the Fab fragment of the monoclonal PLB antibody (anti-PLB Fab) facilitated the formation and increased the length of spontaneous Ca2+ waves (SCWs) originating from the nuclear region in CMs from WT but not from PLB-KO mice. We next examined nuclear Ca2+ activities at basal condition and after sequential addition of IP3, anti-PLB Fab, and the IP3R inhibitor 2-aminoethoxydiphenyl borate (2-APB) at a series of [Ca2+]i. In WT mice, at 10 nM [Ca2+]i where ryanodine receptor (RyR2) based spontaneous Ca2+ sparks rarely occurred, IP3 increased fluorescence amplitude (F/F0) of overall nuclear region to 1.19 ± 0.02. Subsequent addition of anti-PLB Fab significantly decreased F/F0 to 1.09 ± 0.02. At 50 nM [Ca2+]i, anti-PLB Fab not only decreased the overall nuclear F/F0 previously elevated by IP3, but also increased the amplitude and duration of spark-like nuclear Ca2+ release events. These nuclear Ca2+ releases were blocked by 2-APB. At 100 nM [Ca2+]i, IP3 induced short SCWs originating from nucleus. Anti-PLB Fab transformed those short waves into long SCWs with propagation from the nucleus into the cytosol. In contrast, neither nuclear nor cytosolic Ca2+ dynamics was affected by anti-PLB Fab in CMs from PLB-KO mice in all these conditions. Furthermore, in WT CMs pretreated with RyR2 blocker tetracaine, IP3 and anti-PLB Fab still increased the magnitude of nuclear Ca2+ release but failed to regenerate SCWs. Finally, anti-PLB Fab increased low Ca2+ affinity mag-fluo 4 fluorescence intensity in the lumen of NE of nuclei isolated from WT but not in PLB-KO mice.ConclusionPLB regulates nuclear Ca2+ handling. By increasing Ca2+ uptake into lumen of the NE and perhaps other perinuclear membranes, the acute reversal of PLB inhibition decreases global Ca2+ concentration at rest in the nucleoplasm, and increases Ca2+ release into the nucleus, through mechanisms involving IP3R and RyR2 in the vicinity.

Dataset Information

Multiple H⁺ sensors mediate the extracellular acidification-induced [Ca²⁺]_i elevation in cultured rat ventricular cardiomyocytes.

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Multiple H<sup>+</sup> sensors mediate the extracellular acidification-induced [Ca<sup>2+</sup>]<sub>i</sub> elevation in cultured rat ventricular cardiomyocytes.

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